Heating of liquids, for instance water is desirable for a number of applications including personal applications such as bathing, washing or the like, and recreational applications such as in pools, water parks or the like.
In some examples, hot water heaters are used to maintain a quantity of water at a desired set point temperature. The hot water is dispensed on demand, and replacement water within the hot water heater is then heated over time to the desired set point temperature. Hot water heaters have a constant energy demand, even during periods of minimal use (e.g., at night or over vacations). Additionally, hot water heaters use electricity or fossil fuels such as natural gas to heat and maintain the quantity of water at the desired set point temperature.
In other examples, for instance with reservoirs, pools or the like solar covers having a plurality of water filled cavities cover a quantity of water. A solar cover heats the quantity of water and maintains the water at an elevated temperature while the cover is positioned over the water. After removal of the cover, for instance during use of the pool or while providing access to the reservoir, the cover ceases to heat or maintain heat within the quantity of water. Accordingly, to heat or use a pool or other reservoir a user must thereby cover or uncover the quantity of water, and then recover the quantity of water when use is complete.